(a) Field of the Invention
The present description relates to a terminal for periodically transmitting CSI feedback information to a base station.
(b) Description of the Related Art
In a wireless communication system, a first device (e.g., base station) periodically transmits a reference signal (RS) and a second device (e.g., terminal) receives the reference signal to generate a channel state information (CSI) report. The terminal periodically or aperiodically feedbacks the CSI report to the base station on the base of setting of the base station. The CSI report consists of rank indication (RI) of a radio channel, channel quality information (CQI), and a precoding matrix indicator (PMI). The CSI report may be performed by implicit feedback. The RI, the CQI, and the PMI each have different coherence time, and therefore in the wireless communication system, generally, the R1, the CQI, and the PMI are independently encoded and are fed back at separate periods.
When the base station performs elevation beamforming, the terminal uses the reference signal to feedback a horizontal domain CSI (hCSI) and a vertical domain CSI (vCSI) to the base station. In this case, the base station transmits PMI codebook information that may recognize the hCSI and the VCSI to the terminal in advance. The CSI report generated from the terminal may be a 2-dimensional joint CSI at which the hCSI and the vCSI both are calculated or the hCSI and the vCSI separately derived.
When the terminal periodically transmits the CSI report, the terminal uses a unit feedback channel (e.g., physical uplink control channel (PUCCH)). A transmission of one unit feedback channel may be determined as a payload that is equal to or less than the number of bits previously determined to secure uplink coverage.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.